Incandescent lamp.



G. DAVIS.

INCANDESCENT LAMP.

APELICATION FILED s112123. 1w.

vPatented Dec. 23, 19B.

Toallfwomit may-ooncem'." I

l Be it known that I,-'ALBER1 G. DAv1s,-a citizen offthe UnitedVSt'ates, residing at Schenectady, county of# Schenec'tady,- .State of.New York, have invented" certain' new and useful Improvements inIncandescent Lamps', of which the following is a specilicatint `Mylpresent invention-'relates to incandescent electric lamps' and moreparticularlyY to lamps having; filaments of a refractory.

- Incandescentlamp filaments of -tantalum, tungsten, osmium, and similarrefractory elements, are operative at exceedingly high temperatures,andconsequently a't' relatively' high eiiici'encies. Owingto their highAoperating temperature, and'to their small crosssection and somewhatfragile "nature, con'- siderable care must t hej exercised in designingthe lamp in which these -filaments are to run. .The diiiicultie's'l are'different from those experienced With ca`rbonlamps. De#

tails, of construction which have been re.

garded as standard forfcarbonlilamp manul' facture' must inmanyinstances be entirely.

discardedf':

Lamp filaments of the refractory elements above mentioned have aVtendency to' become deformed while' running at :very high temperaturesand `must .ordinarily "be ane chored or otherwise held'in fixed.position with respect-tothelamp bulb. It has heretofore been customaryt-o anchor filament loops by Wires or hooks of refractory material,suchas thoriumv oxid. -Owing to the high running temperature-A of thefilament,l

d-ihicu'lty 'has vbeen experiencedv in. preventing-fusion ofthe filamentto the anchoring device 'andinfl preventing chemical disin egration'ofthe anchoring device induced I 'bythe c lose proximity of the highlyheated metal of 'the 'lilzunent .l A.

` `According to my present invention, certain portions-0f the refractorymetal fila- '.ment are reinforced-1 'or made largelgavith the resulttlatythe reinforced portions radiate more heat than Aother portions andtherefore. remains' at a lower temperature.

.By reinforcing the filament `at the point of support oranchorag'e,,thediiliculty of f uf sion Withtlie` anchor,.or of chemical disspeemcaaonof Lener raten# application mea septmberleaieoz. tsenin 1go; $55,024.

-or material of that 'tungsten is typical.

integratio11eofi" the nchoiing mategigh., is

out more in detail.

A- entirely obvia'tedff'll 'local reinforcements i. offerotheradvantages as lie'reina'f teijpoililld h -Th'e novelfeature's.-of myinvention are particularly pointed -out in the appended scription "takeninconnection with the. ac-

companying drawings..

Yreinforced at -the'point of anchorage; Fig. 3- 1s'.-an enlarged detailshowing" reinforce' ment at-'the point of current supply; and

Figfillustrates a. modification inwhich the. reinforcement is.at theextreme end of the filament loop.

Tungsten Vand some of the other refractory elements above mentionedV areordinarily obtainable in the form of a" non-coherent powder .whichcannot be shaped into filaments or conductors Without the use of somespecial process. In order that my. invention may be readily practised, Ihave hereinafter vdescribed a-'met-hod quiteV suit- -able forthe-manufacture and reinforcement Vof lamp laments of any ofthe-materials fclaimy for'fa better understanding of which,

reference' may` be had to the following ld ee9 above mentioned5 as Wellas of mixtures or lalloys thereof with other'materials; in actf afmethodapplicable t vany-refractory metal The process above mentioned'will bede'- scribed with particular reference to tungsten.

-To secure the reinforcement contemplated` by my present invention,v Iprefer t0- Iiiiali'e use of smalltubes, preferably ofthe samematerial'as the filamennslipped into place on -the filament after thelatter has been completely shrunk and sintered. Tubes suitable for thispurpose may be made by a method quite analogous toV that used 'forthefilament manufacture. obtained b v reduction' oftungsten troxidv withhydrogen accordingto known chemical processes may be employed for theproduction of these tubes. If desir-ed. finely divided tungsten trioxidwhich has been puriied and then ground and sorted may be general class.of whichi;

Tungsten powderi 'comparable tothe diameter of a vlamp fila-' irgent,and finally treat thesetubesto remove. the components 'of 'the binderandto sinterv andshrinlr-the refractory 'residue 'to rend-er.

1t `str-orig and solid. I prefer to use a binder'.

consisting QtaA ductile alloy composed of Vmetals which can Ybe easilyvaporz'ed out ofthe mixt'urerin .order that the resulting liquid may; beentirely' free from carbon.

I' gla'ss tube and heating the tube with a 'Bun- Such a ductil'e alloymay be made by melt-v ing together IlQparts cadmium and 53 parts mercuryand then adding tive parts bismuthf' This alloy can be mixed orimpregliated- With tungsten by nier-ely rubbing the tivo together tvhile the alloy is 1n a. warn;

andplasticstatel- The binder does not'appea-r to chemically combine withthe tung- .tungsten intofthe tube,il" 'maymix the poivi' st en withwhich it :is impregnated., but seems.

to"fo r m a. mechanical mixture by which the particles'of 'tungsten areheld together by the ductilealloy. The applicability' of this-pocess't'o materials other than tungsten is readily apparent. Variousproportions oftungstenand binder may be used, but a mixture-ContainingItungsten 'to the' extent of 30 to..40 per cent. by-Weight of the finalmixture-givesgood results. Such a 'mixture is ductile and pl-iable'andcan be readily rolled or--worked' byany of the metal working processes.TA- squirting temperature ot' l2() tol 150: degrees leentigrade issatisfactory.

The tubes aref'then baked to drive out the mercury'and some of thecadmium, as by placing'th'em grouped'in bundles on apiece ofW1re"Uauze'sup orted in--an evacuated -sen burner. 'lh/lost of; thebismuth andsome Poi the cadmium stay behind with the tung- 'stenin'lthis baking operation. The tubes are nextsuspended' in treatingbottle s.(as', for example, between metallic clamps) and maindergofthebinder.' The treatingbottle should bee'vacua'ted With'a goed mechanicalpump andshoull be maintained dry by the use of an absorbing agent, suchas' phosphorous pentoxid, preferably placed in close proximityto thetube, as in a small dish immedately beneath it. The treatment may beeffected by passing a lowcurrent through the tube fore say, 10 or 15seconds, and then a higher current for. 15. to 30 seconds, or i e've'nfor a minute. A The low current heats it sufficiently to drive out theremainingcadmium and bismuth; andthehigh current sintersl the `residueand shrinks 1t 1n a' compact'homogeneous body havmg a bright the tubesconsist entirelyoffsintered tungquently curve the tvhole into the formshowin short 1 lengths and slipped [on Iover. the .tungsten filaments.to serve-'as local reinforcements. To Asecure the best coperationbetween the reinforcingtube andf'lament, there should be an intimatecontact between thefttvo; .I find, however', that this-close 'unionbetween the parts is easily obtainable; "1t being only necessary to-slip"'the tube in place and thenpass normal' current through thelfilament, whereupon the' filament by 'virtue of its high" temperaturesinters or sticks to. the tube along oneside-fo'r 'at 'several points.The resultant product is about the same as if thejreinforcing tube.-werean 1ntegral'part of. the inclosed filament.

I Filaments locally reinforced as above `de scribedmay be vmounted asshovvn in'Fig. 1

of the drawingzf This gurej shows a lamp provided with fourtllamentloops 1, 2, 3 and 4 provided .with reinforcements 5 for engagement With1' the anchoring hooksv ..l ris-previously indicated, 'these relnfor'cezments serve to-cool vthe filament,l atthe` point ot' anchorage and byfsoA doing prevent dethelament Y In 'addition to the'.localjreinforcements ,above ment1`oned I; may use similarreincomposition of the anchors andfusion with forcements 7 at the endszof each lament' loop Where connection is mad'e with the current-supplywires 8.- This feature lis illus- 'trated .on an' enlargedfscale by Fig.3 of the drawings. Reinforcements at the ends of the filament legs serve*not onlyfto locally 'c colthe filament but also" s'erve'to protect theilamentffroni contamination by the material of the current supply'vWire."` If the' latter be' welded to the filament as shown in Fig.- 3,the 'local enlargement; has the further function of protecting. thefilament from overheatingor oxidation during the weldingoperation. Thisprotection is .secured Aeven though-the'velds be made'with 'greatrapidity andby careless Workmen'. @Fig-4 shows a' somewhat differentapplication of my invention in that the reinforce- Y ment 9 is at theextreme end. of the'tilament loopn-*her'e -it engages with ananchoringorsupporting' .hook .10.- A reinforcement of this sort serves notxonlytolocall'y cool the 'lament, but-.also serves tosep'arate the tw'o legsof the filament-and prevent accidental short-circuit--in caseofslightdeformation' of the filament legs.

In order to construct a curvedlocal reinforcement as shown in Fig. 4,the -process of assembling must be somewhat dijerent from thataboyedescribed. In general, I prefer to make straight tubes andto havethe filament in 'a straight or partially looped condition, and then'slip the tube over the metalic. surface. -When finished, therefore, Efilament to its proper posxtlon 'and subsein Fig. 4 by `Wrapping themembers around with refractory metal' of an anchoring A(lea mandrelheated to a temperature some- `vice loosely engaging said reinforcedbend. 10

what less than red heat. In witness whereof, [I have hereunto set What Iclaim' as new, and desire to secure my hand this `25th day. of..September, 1907. 5 by Letters Patent of the United States, Y ALBERTGr. DAVIS. isl Witnesses: f

` The combination with'a refractory metal BENJAMIN B. HULL, filamentloop having its bend .reinforced HELENO'RFORD.

